1. Field of the Invention
The present invention relates to chain saw sharpening tools and more particularly to a round file holder for use with a chain saw sharpening guide that is operated by engaging the guide with the chain saw cutter bar and the saw chain that is to be sharpened and guiding the file holder during the sharpening process by maintaining the proper angulation of the file secured in the holder with respect to the blade surfaces of the cutter teeth of the saw chain.
2. Description of the Prior Art
Many devices have been developed to assist in the sharpening of chain saws. The principal objective of these sharpening devices is to grip the saw chain and orient the sharpening file with respect to the blade surfaces of the cutter teeth which comprise the chain and maintaining the proper angulation during the sharpening stroke of the file. The file must be angulated in the horizontal plane with respect to the leading or cutting edge of the cutter tooth because the cutting edge is raked with respect to the forward movement of the tooth and the cutter bar of the chain saw.
Thus, attempts by a person to sharpen a saw chain cutter tooth free hand, without the aid of a guide or gauge, are usually ineffective because it cannot be done accurately even by those with a great deal of experience. It is simply too difficult to hold both particular angles accurately for free hand sharpening. The problem is especially exacerbated since the angles must be reversed for each successive tooth as they alternate in their rake and slope with respect to the forward direction of the chain. Almost every person has a preferable orientation for stroking a file, usually depending upon whether they are right handed or left handed, whereby changing orientation to the less preferred angulations causes the file to not be as accurately tracked during the filing stroke as compared with the individual's preferred orientation for manipulating the file.
In order to overcome these problems, many devices have been designed o provided for aiding in the sharpening of saw chains. One particular design which is both simple and effective is described in U.S. Pat. No. 4,864,897 to Charles Newman for a Chain Saw Sharpening Tool issued Sep. 12, 1989. Described therein is a chain saw sharpening tool which includes a channel section having a generally square inverted U-shaped cross-section with a pair of side walls and a connecting wall forming the top of the channel. The channel section is formed for mounting over a saw chain installed in a cutter bar and having an opening formed in the top of the channel section through which the individual teeth of the saw chain can be sharpened. A pair of studs project from the top of the channel adjacent to the opening. The first of the studs is a pivot post for a file guide and the other of the studs is a locator pin. A file holder having a guide means formed along both edges of the holder parallel to the disposition of a file in the holder is provided for engaging a file holder guide. The file holder guide is mounted on the pivot post of the channel section and is formed for engaging the guide means of the file holder. The guide also has locator holes for engaging the locator pin which projects from the channel section. The channel section is placed over the top of the saw chain mounted in the cutter bar of the chain saw. The file holder is engaged with the file holder guide and the guide is oriented with respect to the saw chain by means of the locator pins which engage the file holder guide at the correct position. The file and holder are then reciprocated in their engagement with the file holder guide to sharpen the individual cutter teeth of the saw chain over which the tool has been located.
The problem with the apparatus disclosed in the above-identified '897 patent is that the file holder can only accommodate on diameter file. It is not adaptable to different diameter files for filing different gauge cutting teeth on different sized saw chains. The present invention provides a unique file holder which is readily adaptable to different diameter round files and which can be used with the filing guide disclosed in the '897 patent as well as the improved guide disclosed herein.
More uniquely, the round file holder of the present invention is made from two identical pieces of punched and bent flat steel plate which are arranged in mirror image opposed orientation. The single configuration can be used for both halves of the device, greatly reducing the manufacturing costs, and by its adaptability to different diameter round files, provides a versatility which greatly expands the utility of the filing guide.